Topic
Nuclear quadrupole resonance
About: Nuclear quadrupole resonance is a research topic. Over the lifetime, 3531 publications have been published within this topic receiving 38801 citations. The topic is also known as: Nuclear quadrupole resonance spectroscopy & NQR.
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TL;DR: In this article, experimental data for NQR frequency shifts as a function of temperature reveal a dominant T4 dependence at sufficiently low temperature, T ⪝ 20°K, in accord with a recent prediction.
Abstract: Analyses of experimental data for NQR frequency shifts as a function of temperature reveal a dominant T4 dependence at sufficiently low temperature, T ⪝ 20°K, in accord with a recent prediction. The results indicate the necessity of adding a Debye term to the usual Bayer expression. The coefficient of the Debye term is shown to vary with TD−5; preliminary results indicate that values of the Debye temperature TD may be obtained from low temperature NQR data.
14 citations
TL;DR: The 14N NQR spectra in picolinamide, nicotinamide, isonicotinamide and 2,6‐pyridine dicarboxamide show the presence of two distinct nitrogen positions: the ring position with the quadrupole coupling constant about 4,5 MHz and the amide position about 2.6 MHz.
Abstract: 14N nuclear quadrupole resonance (NQR) frequencies have been measured in picolinamide, nicotinamide, isonicotinamide, 2,6-pyridine dicarboxamide, and acetamide by double resonance. The 14N NQR spectra in picolinamide, nicotinamide, isonicotinamide, and 2,6-pyridine dicarboxamide show the presence of two distinct nitrogen positions: the ring position with the quadrupole coupling constant about 4,5 MHz and the amide position with the quadrupole coupling constant about 2.6 MHz. The NQR data are related to the structure of the investigated compounds and to the NH···O hydrogen bonds. Copyright © 2007 John Wiley & Sons, Ltd.
14 citations
TL;DR: Based on the 14N NQR data, the pπ − dπ interaction in dimethylaminosilanes is weaker than in the amides of phosphorus acids as discussed by the authors.
Abstract: Based on the14N NQR data, the pπ − dπ interaction in dimethylaminosilanes is weaker than in the amides of phosphorus acids.
14 citations
01 Jan 1970
14 citations
TL;DR: In this paper, the spectral properties of trichloroacetic acid complexes with various bases, mainly pyridines and their N-oxides, have been studied and the dependence of the average 35Cl n.q.r. frequencies on ΔpKa has been analyzed in terms of the proton transfer equilibrium.
Abstract: The 35Cl n.q.r. spectra of 29 trichloroacetic acid complexes with various bases, mainly pyridines and their N-oxides, have been studied. The dependence of the average 35Cl n.q.r. frequencies, text-decoration:overlineνQ, on ΔpKa have been analysed in terms of the proton-transfer equilibrium, and the data can be explained either on the basis of a double-minimum potential function with rapid flipping of the proton between two equilibrium sites or one broad minimum. Infrared spectra of such complexes show very broad absorptions over the whole region, with numerous so-called ‘Evans holes’. Variations of the absorption in complexes from the inversion region are similar to those observed in solution. In solids the range of the inversion is shifted to the lower ΔpKa values. Nitrogen and oxygen bases show similar spectral behaviour. In the vicinity of 50% proton transfer the spectral features are similar for A—H…B and A–…HB+ complexes.
14 citations